Method of making a compressed tablet



y 1962 B. J. LEAL ET AL 3,042,531

METHOD OF MAKING A COMPRESSED TABLET Filed Dec. 9, 1959 non-lubricatedcarrier material D L l ILQ t I product material granu a e I tablet clleI (as needed) 1' gl anulate I if necessary J break up v sell discardretalned on le lubrlcatlng tablet" o e lubricant) die surfaces Introduceintroduce Into lnto lubricated tablet die tablet dle compress into Ilubricating tablet" tablet dle operates ll'l cycle of alternatlnglubrlcating tablet compress into production tablet" begin die ejectproduction tablet JITZUKZZEY United States Patent ,042,531 METHOD OFMAKING A COMPRESSED TABLET Bernardine J. Leal, Irvington, and Peter J.Pinto, Union City, Calif., asslgnors to Leslie Salt Company, SanFrancisco, Calif., a corporation of Delaware Filed Dec. 9, 1959, Ser.No. 858,506 Claims. (Cl. 99141) This invention relates to an improvedprocess for making compressed tablets. More particularly, this inventioninvolves a new process of forming firm, smooth, and otherwisepharmaceutically elegant compressed tablets from particulate tabletingcompositions devoid of a tabletdie lubricant. This invention furtherrelates to the products made by this new process.

This application is a continuation-in-part of our application Serial No.842,580, filed September 28, 1959, now abandoned.

In the practice of making compressed tablets for pharmaceutical andother uses, the conventional procedure is to mix the variousingredients, granulate this mixture, lubricate these granules with atablet-die lubricant, and compress the lubricated granules into tabletform. For many purposes, this procedure is very satisfactory and enablestablets of good quality to be produced quickly and cheaply from a widevariety of materials.

However, there are many other occasions when the presence of atablet-die lubricant is deleterious to the finished product. Thefood-canning industry, for instance, often dispenses flavoring materialin tablet form, so that a precise amount is added to each container offood. For example, sugar is commonly added in tablet form when canningpeas, corn, tomatoes, and many other foods. Sugar is well known as oneof the more diflicult materials to tablet, and without a die-lubricanttablets of pure sugar or sugar-containing compositions stick to the die,cap, or easily fracture. However, when the tablet containing lubricantdissolves in the canned-food product, the lubricant contained in thetablet is released; sometimes it coalesces into a globule (as when astearate or other fatty material is used), sometimes it reacts with thecan lining,

and sometimes it even precipitates out and forms a highly unsightlycontaminant throughout the can. Many attempts have been made to overcomethis substantial problem, but none of them have been completelysatisfactory.

Citric acid is another material which is very difiicult to tablet inadequate amounts. When compositions containing percent or more of citricacid are subjected to normal compression pressure, they stick to thetablet-die. When the pressure is reduced, the compositions fail to forminto a tablet, or form one which is extremely soft and crumbly.

This die-lubricant problem presents itself in yet another manner;namely, when a lubricant is admixed with a tableting composition, onlythe very small portion of the lubricant in contact with the die-cavityperforms its intended function. The rest of the lubricant does nolubrication; it is wasted and only present because, heretofore, no oneknew how to get the desired lubrication without distributing thelubricant evenly in the tableting composition.

In large-scale tableting operations, much lubricant material is used,involving substantial expense. Therefore, it means could be devised toplace the lubricant only at the granule-die interface, much lesslubricant would be consumed in the process and a considerable savingwould be I achieved. Furthermore, the resulting tablet would containless inert material and therefore a greater percentage of active agents.

An important object of this invention, therefore, is to provide aprocess for making compressed tablets without 3,042,531 Patented July 3,1962 2 incorporating a tablet-die lubricant in the composition to betableted.

A further object of this invention is to provide a process of forming apharmaceutically elegant compressed tablet from powdered or granulartableting compositions containing no die-lubricant, even though thecompositions have a normal tendency to stick in the die-cavity, cap,split, or otherwise result in deformed tablets.

A still further object of this invention is the provision of a means oflubricating the die-cavity in a-compressedtablet-making machine otherthan by including a dielubricant in the tableting compositions to becompressed therein.

A further object of this invention is to achieve a major reduction inthe amount of die-lubricant used in the manufacture of compressedtablets.

These and other objects have been achieved by applying a conventionaltablet-die lubricant directly to the walls of the die-cavity immediatelypreceding the introduction into the die-cavity of the material to becompressed into a tablet. By this process, a pharmaceutically elegantcompressed tablet may be formed from any tableting composition, nomatter how difficult to tablet, without previously incorporating adie-lubricant.

This process, in fact, eliminates the presence of practically all thedie lubricant in the finished tablet, for no lubricant exists inside thetablet but rather only on its surface, and then in an extremely smallamount. This means a new product is provided, at a considerable savingin the amount of lubricant formerly needed.

One of the more valuable advantages in the use of this process is thatpharmaceutically elegant tablets, of materials heretofore extremelydifficult to compress into tablets, may now be formulated withoutinclusion of an objectionable amount of die-lubricant. When tablets madeby this process are used in flavoring canned goods, no objectionableprecipitation or coalescing of the lubricant material occurs, no harmfulreacting with the lining of the container takes place, and no otherundesirable conditions associated with lubricants arise.

Other objects and advantages of the invention will appear from thefollowing description of some preferred embodiments thereof.

The drawing is a flow-sheet depicting the processes of the invention.

In general, our process comprises applying a minute amount ofdie-lubricant to all the tablet-contacting surfaces of the die (that is,the die-cavity and the heads of the upper and lower punches),immediately preceding the introduction into this space of thenon-lubricated material for forming the tablet. Coating the die, as allthese surfaces will be termed henceforth, is accomplished by compressingtherein a lubricated carrier material and then ejecting the so-formedlubricating" tablet. Next, the product composition devoid of lubricantis introduced into this same die and compressed into a productiontablet. The compression of the lubricated carried mate rial results indepositing a minute amount of the lubricant on the surfaces of the die.When this lubricating tablet is ejected, enough lubricant is left behindto lubricate the die for compression of the product composition which isdevoid of lubricant. This amount of residual lubricant on the die afterejection of the lubricating tablet, but before introduction of theproduct composition, is sufficient for production of .a pharmaceuticallyelegant tablet from any tableting composition, without danger ofcapping, splitting, or adhesion thereof to the die surfaces. Althoughthe production tablets made by this process do contain a very slightamount of lubricant, it is only upon their surfaces and, as such,constitutes a most minute proportion of the total tablet.

Our invention is graphically illustrated in the accompanying drawing.Starting with the carrier material, which may or may not requiregranulation, depending on the nature of the carrier (i.e., salt does notneed to be granulated), it is first lubricated by admixing with atablet-die lubricant. This lubricated carrier material is thenintroduced into a die-cavity of a compressed-tabletmaking machine andcompressed into a so-called lubricating tablet. The lubricating tabletis then ejected from the die and may be discarded, sold, or broken up(as-by crushing or, where the tablet is soft, dropped onto a hardsurface) and used again to form another lubricating tablet. If thelatter procedure is chosen, it is necessary periodically to replenishwithin the broken lubricatingtablet material uflicient lubricant tomaintain a proper carrier material-lubricant ratio. Also, if some brokenmaterial, or whole lubricating tablets, are lost or spilled, freshcarrier-material may be added to rebuild the supply.

Following ejection of the lubricating tablet, the nonlubricated productmaterial, in particulate (i.e., powder, granular, etc.) form, isintroduced into the die and compressed into a so-called productiontablet. This production tablet then is ejected from the die, coming outeasily without capping or otherwise breaking, to complete one cycle ofthe machine and place the die in position for receiving another portionof lubricated carrier material. The cycle is therefore lubricatingtablet-then production tablet, and it is repeated for as many tablets asneed to be made. This cycle, of course, is the same for each die in themachine, whether it be one or a great number, such as found in thelarger rotary-head machines capable of producing thousands of tabletsper minute. In every case, the process works to complete satisfaction,providing pharmaceutically elegant tablets from any tabletingcomposition.

As a carrier-material for the lubricant, any composition may be usedwhich is adaptable for compression into tablet form, and which will notcontaminate, in an objectionable manner, the production tablet. Forinstance, since the canning industry makes use of large amounts of saltin fiavorings, and since sodium chloride itself is quite easy to tablet,granular sodium chloride is a satisfactory carrier for the lubricant. Ifany of the chloride material is carried over by chance into theproduction tablet, it will not destroy the utility of the tablet,especially if the contamination is very small. A host of othermaterials, such as potassium chloride, calcium chloride, sodium borate,sugar, vegetable meals, grains, wetting agents, etc., may also be used.

It is possible to combine the manufacture of two different marketabletablets into this one cycle by forming the lubricating tablets frommaterials which are saleable. For instance, where there is a market forsalt tablets containing a lubricant, the above-mentioned sodium chloridelubricating tablet takes the added status of a second production tabletwhile retaining its lubricating tablet status. This, of course, can bedone with other compositions as Well.

Carrier material of a wide range of particle sizes may be utilized inthis process, depending on the size of the tablet to be made, themachine, and other factors. Where sodium chloride is used, excellentresults are obtained if the fines are eliminated. Medium, kiln-dried,granular sodium chloride has been found highly satisfactory. This is amixture of granules as set forth in the following Table I.

TABLE I Medium, Kiln-Dried, Granular, Sodium Chloride Approximatepercent of total $126 of screen: granulation passing 6-mesh 100 8-mesh98 l-mesh 56 l4-mesh l -mesh 1 All meshes U.S. Tyler.

Any conventional tablet-die lubricant may be used in this new process.For instance, white mineral oil (U.S.P.) containing a very small amountof sodium stearate is quite satisfactory. Although in some instances itmay be more desirable to eliminate all of the stearate, it has beenfound that the mineral oil-sodium stearate mixture generally givesbetter results than mineral oil alone. The amount of sodium stearateincorporated in the mineral oil is widely variable, depending upon thecomposition to be compressed into the production tablet.

One satisfactory lubricating tablet comprises the abovementionedkiln-dried salt granules lubricated with approximately 2.0 percent,based on the final weight of the lubricating tablet, of a mineraloil-sodium stearate mixture, with the sodium stearate constituting about0.08 percent of the final weight of the lubricating tablet. Thislubricating tablet leaves behind on the die surfaces sulficientlubricant to insure proper lubrication of at least one productiontablet, no matter what the composition of the production tablet may be.The amount of mineral oil-sodium stearate retained by these productiontablets is negligible. Tests on these production tablets showed nodetectable precipitation of this lubricant in various media, andreactions between food containers or their linings and this lubricantalso were absent. Satisfactory lubricating tablets may be formed, also,from the aforementioned carrier granules, and such lubricants asstearates (e.g., sodium, calcium, and magnesium) alone, Sterotex(hydrogenated vegetable oil), various vegetable oils, polyethyleneglycols, lecithin, hydrated calcium silicate, and many others.

The particle size of the material used in making the production tabletsis not critical. Substantially all particle sizes within the realm ofconventional tableting techniques, that is, from the finest powder tothe coarsest granule, are operable, and mixtures of different particlesizes also are feasible. Not only may production tablets be made withthis process from solid ingredients, but liquid components, such asspice extracts, also may be tableted if admixed with sufficient solidmaterial.

The pressures used in the tableting operations also are variable, withall of the standard tableting pressures giving satisfactory results.Rather than having to adjust the pressure to a point intermediatebetween that producing capping and that producing a soft tablet, thisprocess enables tablets of a wide range of hardness or softness to beproduced without objectionable fracturing or other damage.

The invention also is operable with all types ofcompressed-tablet-making machines. Furthermore, the composition of thedies and punches is not critical, since plain steel, carbide, stainlesssteel, and all other dies and punches carry out the methodsatisfactorily. Carbide dies and punches have given, in general, thebest results.

Where the lubricating tablets are not marketable, and their primary useis to impart a thin, film-like coating of lubricant to the die, it isentirely practical to recover them, break them, granulate the brokenmaterial if necessary, and use this recovered material to form morelubricating tablets. Naturally, as this is done repeatedly theproportion of lubricant will be diminished and replenishment thereoffrom time to time is necessary. Once a workable amount of carriermaterial is established, and

properly lubricated, the only significant additional cost is for theslight amount of lubricant needed to maintain the material-lubricantratio. As is apparent from the minute amount of lubricant retained bythe production tablet, this constitutes a very small figure. Of course,where economics are suitable, it is entirely feasible to discard thelubricating tablet.

The following examples are set forth to better illustrate the invention,with the understanding that they are not to be construed as a limitationin any manner upon the broad concept disclosed herein,

EXAMPLE 1 Tablets containing 67.3 percent sugar, 30.7 percent salt, and2.0 percent of a liquid spice extract were prepared following theprocess of this invention. Lubricating-tablet granules of mediumkiln-dried sodium chloride were lubricated with approximately 2.0percent, based on the final weight of the lubricating tablet, of acomposition comprising white mineral oil (U.S.P.) and sodium stearate,the sodium stearate constituting approximately 0.08 percent of the finalweight of the lubricating tablet. A conventional rotary-headcompressed-tabletmaking machine, with a plurality of dies arranged tocompress and eject two tablets per die per revolution of the head, wasused. One granulation hopper was filled with the lubricated saltgranules and the other hopper filled with the granulatedsugar-salt-spice extract production-tablet composition. The machine wasset for 1500 tablets per minute, and a cycle of lubricating tablet-thenproduction tablet was established in each die. Over 10,000production-tablets were made by this procedure, all of which wereperfectly formed, whole, and none of which capped or stuck to thetablet-dies. This is in contrast to prior attempts of tableting the samesugarsalt-spice extract composition using the techniques of the priorart, which resulted in sticking and capping after three or fourrevolutions of the die-head.

The production-tablets so formed ultimately were shipped to a canner whoused them in canning vegetables,

and tests showed no trace of stearate precipitates and no evidence of adeleterious reaction with the containers or their linings. Theproduction-tablets were quick to dissolve in the canned medium, to givea pleasant and satisfactory taste without any undesirable foreignmatter.

EXAMPLE 2 In response to a request for pure sugar tablets, 100 percentgranulated sugar was used to form the production-tablet. Thelubricating-tablet composition was the same as that of Example 1. Thegreat difliculty in compressing 100 percent sugar into tablet form iswell known, especially when no lubricant is applied to the sugargranules, and it was expected that problems would be encountered.However, a tablet-machine of the same type as that described in Example1 was set at a rate of 1500 tablets per minute, the production-tablethopper filled with the 100 percent sugar granules and thelubrieating-tablet hopper filled with the lubricated salt granules. Thesame lubricating tablet-then production tablet cycle of Example 1 wasperformed without any tablets capping, splitting, or sticking; and theproduction-tablets, as well as the lubricating-tablets, werepharmaceutically elegant.

EXAMPLE 3 The inventive process also has been carried out on acomposition comprising approximately 30.0 percent salt, 65.7 percentsugar, 2.4 percent calcium chloride and 1.9 percent spice extract, inconjunction with the lubricating-tablet mixture of Examples 1 and 2. Thesame tableting-machine of Examples 1 and 2 was used, theproduction-tablet hopper was filled with the salt-sugarcalciumchloride-space extract composition and the lubricating-tablet hopperfilled with the lubricated salt granules. Following the lubricatingtablet-then production tablet cycle of Examples 1 and 2, the machineproduced pharmaceutically perfect tablets without jamming, withouttablets sticking in the die-cavity, and with no evidence of capping orsplitting.

EXAMPLE 4 Production-tablets containing approximately 34.5 per.- centsalt, 64.0 percent sugar, and 1.5 percent granular garlic were madefollowing the process of this invention. The lubricating-tabletcomposition of Examples l-3 was used. A double-punch tableting-machinelike that of the preceding examples was employed to form tablets from 6these compositions on a repeating lubricating tablet-then productiontablet cycle. All the tablets so formed were structurally sound,pharmaceutically elegant in appearance, with no evidence ofimperfection. Furthermore, the machine did not jam or malfunction onceduring the run.

EXAMPLE 5 A composition consisting essentially of 65.2 percent sugar,32.8 percent salt, 1.9 percent granular garlic, and 0.1 percent granularcayenne pepper was compressed into production-tablets with the processof this invention. The lubricating-tablet, the tablet-making machine,and the procedural steps were the same as in the preceding examples.These flavoring tablets were uniformly excellent in structure andappearance, and no difiiculties in the operation of the machine wereencountered.

EXAMPLE 6 To determine the operability of several lubricating tabletcompositions, production tablets were formed from a mixture of percentsugar and 25 percent salt, using the following compositions in Table IIfor lubricating the die. In each instance, both the lubricating-tabletand the production-tablet were well-formed, did not stick or bind in themachine, and otherwise very satisfactory.

TABLE II Lubricating-Tablet Compositions Composition Component Amount32.5 lbs. 0.5 qt. 32.0 lbs. 0.5 qt. 32.5 lbs. 0. t.

10 sal 32.5 lbs.

glyceryl monostearate- 1.5 lbs.

11 salt 32.5 lbs.

Stcrotex (hydrogenated vegetable oils) 12.0 oz.

12 s 32.5 lbs.

cocoa butter 8.0 oz.

13 sugar 32.5 lbs.

mineral oil 05 qt.

14 {linseed meal 5.0 lbs.

sodium stearate. 4.0 oz.

15 {alfalfa (ground)- 5.0 lbs.

glyceryl monostcarat 1.0 lb.

16 polyethylene glycol (average molecular 7.0 lbs.

weight-4,000).

17 {who 5.0 lbs.

mineral oil. 2.0 oz. cottonseed meal 5.0 lbs.

18 sodium stearate 2.0 oz. tri-calcium phosphate 1.0 oz.

19 soyabean meal 5.0 lbs.

Sterotex 1.0 oz.

20 {barley 5.0 lbs.

sodium stearate 2.0 oz.

EXAMPLE 7 encountered and the machine performed smoothly and freely.

EXAMPLE In an attempt to make tablets of pure citric acid, a compositioncomprising 32.5 lbs. salt and 2.0 oz. sodium stearate was utilized asthe material for lubricating the die. The cyclic procedure oflubrication tablet-then 75 production tablet was followed. Theproduction-tablets 7 did not stick in the die or otherwise interferewith the operation of the machine, but because of the nature of purecitric acid (hydrous) these tablets were quite soft. Thelubricating-tablets were well-fomed and also presented no problem to theoperation of the machine,

EXAMPLE 9 Tablets of pure sugar have been made by the process of thisinvention, using a mixture of 32.5 lbs. of sugar and 0.5 qt. of mineraloil as the lubricating-tablet composition. Both the pure sugar and thesugar-mineral oil composition compressed into pharmaceutically eleganttablets without any sticking in the die or malfunctioning of themachine.

The preceding examples illustrate the versatility of the new processherein disclosed. It may be used with great success with varioustableting speeds and tablet dies. It lends itself equally well tocompositions easy to tablet and those difficult to tablet, and producesexcellent results in either case. Because of the absence of sticking andjamming of the machine, wear and tear on the machine is considerablyreduced when using this process, and the speed of the machine may beincreased appreciably because of this consistently smooth operation,

This process is operable for making any conventional compressed tableWhere it is desired to eliminate all or practically all of the lubricantfrom the final product. It is not sensitive to any particular tabletingcomposition, so long as the composition is reasonably susceptible tocompression into tablet form.

To those skilled in the art to which this this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

We claim:

1. A process for manufacturing compressed tablets, comprising:introducing into a tablet-diet a first composition comprising atableting material lubricated with a pharmaceutical tablet-dielubricant; compressing this said first composition into a lubricatingtablet; ejecting this said lubricating tablet; introducing into the sametabletdie a second composition comprising a non-lubricated tabletingmaterial; compressing this said second composi tion into a productiontablet; ejecting this said production tablet; and repeating the cycle oflubricating tablet-then production tablet until a desired amount oftablets is formed.

2. A process as defined in claim 1, wherein the lubricating tablets areformed from a marketable composition.

3. A process as defined in claim 1, wherein the lubricating tablets arebroken and the broken material used to form new lubricating tablets,

4. A process as defined in claim 3, wherein the broken material isgranulated.

5. A process as defined in claim 3, wherein the desired ratio oflubricant in the lubricating-tablets in maintained by periodic additionof fresh lubricant to the broken material.

6. A process as defined in claim 1, wherein the dielubricant is selectedfrom the group consisting of mineral oil, vegetable oils, waxes,hydrogenated vegetable oils, alkali metal stearates, alkali earth metalstearates, alkali metal benzoates, and mixtures thereof.

7. A process as defined in claim 1, wherein the dielubricant is amixture of white mineral oil and sodium stearate.

8. A process as defined in claim 1, wherein the dielubricant is sodiumstearate.

9. A process as defined in claim 1, wherein the particulate material isselected from the group consisting of salt, sugar, wheat, barley,linseed meal, soyabean meal, and ground alfalfa.

10. A process for manufacturing compressed sugar tablets, comprising:introducing into a tablet-die a first composition comprising granularsodium chloride lubricated with a pharmaceutical tablet-die lubricantselected from the group consisting of mineral oil, vegetable oils,waxes, hydrogenated vegetable oils, alkali metal stearates, alkali earthmetal stearates, alkali metal benzoates, and mixtures thereof;compressing this said first composition into a lubricating'tablet;ejecting this said lubricatingtablet; introducing into the sametablet-die a second composition comprising non-lubricated sugarparticles; compressing this said second composition into a sugar tablet;ejecting this said sugar tablet; and repeating the cycle of lubricatingtablet-then sugar tablet until a desired amount of tablets are formed.

11. A process as defined in claim 10, wherein the lubricating-tabletsare broken and the broken material used to form new lubricating tablets.

12. A process as defined in claim 11, wherein the desired ratio oflubricant in the lubricating-tablets is maintained by periodic additionof fresh lubricant to the broken material.

13. The process of claim 10, wherein the lubricatingtablet comprisesabout 98.0 percent sodium chloride and 2.0 percent lubricant.

14. The process of claim 13, wherein the lubricant comprises whitemineral oil (U.S.P.) and sodium stearate.

15. A method of tablet production wherein two different tabletingcompositions are compressed, alternately, in the same tablet-die, one ofthe said compositions containing a tablet-die lubricant and the othersaid composition being devoid of tablet-die lubricant.

References Cited in the file of this patent UNITED STATES PATENTS1,289,570 Stokes Dec. 31, 1918 2,046,833 Meyer July 7, 1936 2,444,282Creevy June 29, 1948 2,735,380 Bowes Feb. 21, 1956 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3,042,531 July 3, 1962Bernardine J. Leal et a1.

rror appears in the above numbered pat- It is hereby certified that eetters Patent should read as out requiring correction and that the saidL corrected below.

Column 7, line 4, for "well-fumed" read well-formed 11ne 39, for"tabletdiet" read tablet-die Signed and sealed this 30th day of October1962.

(SEAL) Amt:

DAVID L. LADD ERNEST W SWIDER Commissioner of Patents Attesting ()ffieer

1. A PROCESS FOR MANUFACTURING COMPRESSED TABLETS, COMPRISING:INTRODUCING INTO A TABLET-DIET A FIRST COMPOSITION COMPRISING ATABLETING MATERIAL LUBRICATED WITH A PHARMACEUTICAL TABLET-DIELUBRICANT; COMPRESSING THIS SAID FIRST COMPOSITION INTO A LUBRICATINGTABLET; EJECTING THIS SAID LUBRICATING TABLE; INTRODUCING INTO THE SAMETABLETDIE A SECOND COMPOSITION COMPRISING A NON-LUBRICATED TABLETINGMATERIAL; COMPRESSING THIS SAID SECOND COMPOSITION INTO A PRODUCTIONTABLET; EJECTING THIS SAID PRODUCTION TABLET; AND REPEATING THE CYCLE OF"LUBRICATING TABLET-THEN PRODUCTION TABLET" UNTIL A DESIRED AMOUNT OFTABLETS IS FORMED.